Research on Coal Tar Pitch Catalytic Oxidation and Its Effect on the Emission of PAHs during Co-Carbonation with Coal

Coal tar pitch (CTP) is abundant and widely used, but its properties will be affected due to oxidation aging during storage. In this study, CTP was oxidized by simulating the air oxidation process, and the change of chemical structure has been analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and both gas chromatography and mass spectrometry (GCMS). The effects of the oxidized and unoxidized CTP co-carbonization with coal on the polycyclic aromatic hydrocarbons (PAHs) emission were detected by GCMS. The small and medium-molecule aromatic substances were reduced during CTP oxidation, while the intermolecular condensation reaction increased the macromolecules content. The catalytic can effectively facilitate the dehydrogenation and condensation reaction of CTP and the entry of oxygen molecules, which leads to the increase of oxygen-containing groups and the decrease of PAHs. Compared to the raw CTP, the catalytic oxidized CTP significantly reduced the emissions of toxic PAHs during the co-carbonization with coal. A possible catalytic mechanism of CTP catalytic oxidation is proposed.

Study of the phase transition ability of coal tar pitch and their coke products under the influence of temperature used to synthesise carbon composite materials

Using differential scanning calorimetry and thermogravimetric analysis showed the marking temperature of coal tar pitch is 107.8°C. The thermal decomposition of the pitch is divided into three main stages, corresponding to three phases α, β, γ, with a coke yield of 47% at 800°C. The change in the XRD diagram showed a clear transition from the amorphous state of carbon to the highly ordered crystalline structure of graphite after treatment at 2,200 and 2,700°С. The purity of the pitch sample and the structure of the CCC carbon-carbon composite material after heat treatment at 2,700°C were studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy methods. The results showed that after heat treatment, the C content in the sample reached more than 99.5%, and the coke residues after graphitization were bound and connected to the carbon fabric into a mass of graphite material.

Preparation of Isotropic Carbon Fibers from Kerosene-Purified Coal Tar Pitch by Co-Carbonization with Pyrolysis Fuel Oil

An inexpensive and general-purpose carbon fiber was prepared using coal tar pitch. In contrast to the solvent extraction process employing expensive solvents, a low-cost centrifugal separation method facilitated the reduction of loss due to the pitch purification and an overall yield increase. The coal tar pitch purified by centrifugation and subsequently co-carbonized with pyrolysis fuel oil improved in spinnability. Moreover, the resulting spinnable pitch had a softening point of 250 °C. The obtained carbon fibers were heat-treated at 1000 °C for 5 min, resulting in a tensile strength of approximately 1000 MPa and an average diameter of 9 μm. In this study, we present an effective method for obtaining low-cost general-purpose isotropic carbon fibers.